reading through the factorio devblogs for the in-development 2.0 release and came across this gem:

> Often times you want to set some constant number, like "I want 7.5 stacks here", and doing the calculation MANUALLY is of course unacceptable. So we made it that you can type mathematical expressions directly in the textfields.

woooooooooooooooooo finally! numeric text inputs will let you type "100/3" or "50+80" or "10^6" and it'll be properly evaluated.